Prosthetic joints comprise an adjustable link designed to interconnect adjoining members of a prosthetic limb. By way of example, an adjustable prosthetic link can be used to interconnect adjoining prosthetic members such as a stump support and a thigh member, a knee joint and a member forming a lower leg, or at the ankle of the prosthetic device for connecting the lower end of a lower leg member and an artificial foot. Other examples of uses of adjustable prosthetic joints are known to those skilled in the art.
In a prosthetic leg, for example, the body structure of the user and his attitude when standing or walking may require certain adjustments in the relative position of various components in the artificial leg. Frequently, these adjustments must be made in two mutually orthogonal planes: in the anterior-posterior plane and in the lateral-medial plane. In the prior art, the use of a universal joint of the ball and socket type for this purpose was inconvenient because it provided no stability against rotation about the major axis of the limb. Once dislodged, the assembly could not be accurately returned to its original position without the help of external references.
On the other hand, prior attempts at solving the problem by a cross hinge articulation resulted in cumbersome and relatively expensive structures.
U. S. Pat. No. 3,659,294 to Glabiszewski, assigned to Otto Bock of West Germany, discloses a very successful prosthetic link mechanism for enabling relative adjustment of two members of a prosthetic limb in two mutually orthogonal planes, while avoiding the disadvantages then prevalent in the prior art.
The Otto Bock adjustable prosthetic link included a male and female part, respectively, on two artificial limb members to be relatively adjusted, one of the parts having two pairs of contact surfaces which are bisected by mutually orthogonal planes, the other part having adjustable abutment means such as set-screws engaging these surfaces for retaining the two parts in a selected angular position within predetermined swing ranges in the two planes. More specifically, the male part had a spherically convex base from which a substantially frustopyramidal boss rises divergingly and the female part comprised an annular socket. The contact surfaces on the male part comprised the respective sides of the preferably four-sided frustopyramid. The set-screws bearing upon these sides extended at right angles and were lodged in the socket for engaging the contact surfaces of the boss for retaining the component parts in a selected angular position within predetermined swing ranges.
This adjustable link has been used for a number of years as a means for setting the angular relationship between component parts at various joints in a prosthetic limb. However, adjustment and readjustment of this link and other prosthetic components can be a cumbersome and time-consuming procedure. For instance, the prosthetist often is required to take apart a prosthetic device and then put it back together again, such as when correcting the device when a bushing wears out, when a new component is added, if a component breaks, or if the device becomes loose from wear. When the prosthetic device is reassembled, the adjustable joint or joints which have been disassembled must be reassembled and realigned. The alignment process for the Otto Bock joint, for example, requires settings in the anterior-posterior and the lateral-medial planes. In the past, the Otto Bock joint has been realigned by keeping track of the amount of rotation of each of the four set screws, although this is not always a desirable or foolproof method. Moreover, after reassembling the new prosthetic device, if an adjustable prosthetic link must be reset, the patient must walk with the new device to test whether the realignment is correct, and then through trial and error the device may be properly aligned.
The present invention takes the guess work out of the realignment procedure and provides a means for quickly and easily realigning an adjustable prosthetic joint.